Compressor having a cooling circuit and corresponding cooling method

The invention includes a method of cooling a compressor and resides in a compressor (2) which comprises a rotor (4) having a plurality of stages (6), each of the plurality of stages (6) including a set of radially extending rotor wheels (8); a working fluid supply path (10) for providing working fluid to each of the plurality of stages (6) for compression by each set of radially extending rotor wheels (8); a purge circuit (12) for diverting a first portion of the working fluid from an upstream portion (14) of the working fluid supply path (10) to at least one downstream stage (16) of the plurality of stages (6); and a substantially axial bypass path (18) bypassing the at least one downstream stage (16), the substantially axial bypass path (18) for diverting a second portion of the working fluid around the at least one downstream stage (16).